Electrosurgical dissector with thermal management

ABSTRACT

An electrosurgical dissection apparatus is disclosed, and includes a thermally insulating body, a thermally conductive insert, at least one active electrode, and at least one return electrode. The at least one active electrode is disposed on the thermally conductive insert, and the at least one return electrode is spaced from the at least one active electrode by a portion of the thermally insulating body. The thermally conductive insert is configured to cauterize tissue dissected by radiofrequency energy passing from the at least one active electrode to the at least one return electrode.

CROSS REFERENCE TO RELATED APPLICATION

The present patent application is a divisional of U.S. patentapplication Ser. No. 15/679,398, filed Aug. 17, 2017, now U.S. Pat. No.10,206,732, which is a divisional of U.S. patent application Ser. No.13/898,601, filed May 21, 2013, now U.S. Pat. No. 9,757,181, whichclaims the benefit of and priority to U.S. Provisional PatentApplication Ser. No. 61/658,523, filed on Jun. 12, 2012. The entirecontents of each of the foregoing applications are hereby incorporatedherein by reference.

BACKGROUND Technical Field

The present disclosure relates to an electrosurgical dissection systemand method for performing electrosurgical dissection procedures. Moreparticularly, the present disclosure relates to a system and method fortransmitting radio frequency energy from an electrosurgical generator toa treatment site through a dissector formed of materials having thermalprofiles allowing for the selective storage and deposit of thermalenergy into surrounding tissue.

Background of Related Art

Electrosurgery involves application of high radio frequency electricalcurrent to a surgical site to cut, ablate, or cauterize tissue, or tocoagulate blood. In monopolar electrosurgery, a source or activeelectrode delivers radio frequency energy from the electrosurgicalgenerator to the tissue and a return electrode carries the current backto the generator. In this configuration, the active electrode istypically part of a surgical instrument held by the surgeon and appliedto the tissue to be treated. A patient return electrode is placedremotely from the active electrode to carry the current back to thegenerator.

In bipolar electrosurgery, one of the electrodes of a hand-heldinstrument functions as the active electrode and the other as the returnelectrode. The return electrode is placed in close proximity to theactive electrode such that an electrical circuit is formed between thetwo electrodes (e.g., electrosurgical forceps or electrosurgicalpencils). In this manner, the applied electrical current is limited tothe body tissue positioned between the electrodes. When the electrodesare sufficiently separated from one another, the electrical circuit isopen and thus inadvertent contact of body tissue with either of theseparated electrodes prevents current flow.

Since electrosurgical procedures generate thermal energy through theactive electrode, the absorption and storage of thermal energy by theelectrosurgical pencil body is of particular importance. When the activeelectrode is not receiving power or is between cycles in AC powergeneration, thermal energy stored in the electrosurgical pencil body istransmitted to surrounding tissue. It is desirable to provide anelectrosurgical pencil having a body with a thermal profile thatprovides for the controlled and directed release of thermal energy intosurrounding tissue.

SUMMARY

As used herein, the term “distal” refers to that portion that is furtherfrom an operator while the term “proximal” refers to that portion thatis closer to an operator. The term “dissection” may refer to cutting,ablating, or cauterizing tissue, and may additionally refer to theresultant coagulation of blood therefrom.

As used herein the term “electrosurgical pencil” is intended to includeinstruments which have a handpiece which is attached to an activeelectrode and which is used to dissect tissue. Typically, theelectrosurgical pencil may be operated by a handswitch or a foot switch.The “active electrode” is an electrically conducting element which isusually elongated and may be in the form of a thin flat blade with apointed or rounded distal end.

As used herein, the terms “energy” and “electrosurgical energy” refersbroadly to include all types of energy used to treat tissue, e.g., RFenergy, ultrasonic energy, microwave energy, thermal energy, lightenergy, etc.

According to one aspect of the present disclosure, an electrosurgicaldissection apparatus is disclosed, and includes a thermally insulatingbody, a thermally conductive insert, at least one active electrode, andat least one return electrode. The at least one active electrode isdisposed on the thermally conductive insert, and the at least one returnelectrode is spaced from the at least one active electrode by a portionof the thermally insulating body. The thermally conductive insert isconfigured to cauterize tissue dissected by radiofrequency energypassing from the at least one active electrode to the at least onereturn electrode.

In one aspect of the present disclosure, the at least one activeelectrode may be formed from copper, silver, or gold. In another aspectof the present disclosure, the at least one active electrode may beformed from a coating of conductive material such as copper, silver, orgold.

In another aspect of the present disclosure, the thermally insulatingbody may be formed from an amorphous polyamide. In one aspect of thepresent disclosure, the thermally conductive insert may be formed fromalumina.

In a further aspect of the present disclosure, the electrosurgicaldissection apparatus further includes at least a pair of approximatablejaw members each including a sealing plate. Each of the at least oneactive electrode and the at least one return electrode may be disposedon a respective opposing sealing plate.

According to another aspect of the present disclosure, anelectrosurgical dissection system is disclosed, and includes anelectrosurgical generator and an electrosurgical dissection apparatus.The electrosurgical dissection apparatus includes a thermally insulatingbody, a thermally conductive insert, at least one active electrode, andat least one return electrode. The at least one active electrode isdisposed on the thermally conductive insert, and the at least one returnelectrode is spaced from the at least one active electrode by a portionof the thermally insulating body. The thermally conductive insert isconfigured to cauterize tissue dissected by radiofrequency energypassing from the at least one active electrode to the at least onereturn electrode. In another aspect of the present disclosure, the atleast one active electrode is electrically coupled with theelectrosurgical generator.

In one aspect of the present disclosure, an electrosurgical dissectionapparatus comprises a body defining a longitudinal axis and includes aplurality of electrodes, a thermally insulating portion, and a thermallyconductive portion proximal of the thermally insulating portion. Thethermally conductive portion is configured to store thermal energygenerated by at least one electrode of the plurality of electrodes forrelease into tissue.

In another aspect of the present disclosure, the body may have a taperedprofile. In yet another aspect of the present disclosure, at least oneelectrode of the plurality of electrodes may be coated with anelectrically conductive material. In another aspect of the presentdisclosure, the thermally conductive portion of the body may be formedof alumina. In still another aspect of the present disclosure, thethermally insulating portion may be formed of an amorphous polyamide.

In another aspect of the present disclosure, a method of using anelectrosurgical apparatus having an active electrode, a returnelectrode, and an electrically insulating section is disclosed. Themethod includes supplying current between the active electrode and thereturn electrode such that tissue is dissected. The method also includescauterizing tissue with thermal energy stored in the electricallyinsulating section.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure are described herein withreference to the drawings wherein:

FIG. 1 is a perspective view of the presently disclosed electrosurgicaldissection system including an electrosurgical pencil coupled to anelectrosurgical generator;

FIG. 2 is a cross-sectional view taken along section line 2-2 of FIG. 1;

FIG. 3 is an enlarged detail view of the distal tip portion of theelectrosurgical pencil of FIG. 1, and showing the formation of an activeelectrode by a micropen;

FIG. 4 is a top view of the electrosurgical pencil with electricalcurrent flowing from the active electrode to the return electrodes, andprior to insertion into tissue;

FIG. 5 is a top partial view of the active electrosurgical pencil shownin FIG. 4, inserted into a layer of tissue;

FIG. 6 is a top partial view of the electrosurgical pencil as shown inFIG. 5, with the electrodes inactive and a thermally conductive insertradiating thermal energy to the surrounding tissue;

FIG. 7 is a top partial view of an alternate embodiment of anelectrosurgical pencil, with electrical current flowing from a pluralityof active electrodes to a plurality of return electrodes, and insertedinto a layer of tissue;

FIG. 8 is a top partial view of the electrosurgical pencil as shown inFIG. 7, with the electrodes inactive and a thermally conductive portionradiating thermal energy to the surrounding tissue;

FIG. 9 is a perspective view of an alternate embodiment of anelectrosurgical pencil having a tapered body and corresponding thermalprofile;

FIG. 10 is a perspective view of an electrosurgical apparatus accordingto the present disclosure;

FIG. 11 is a perspective detail of the jaw members of theelectrosurgical apparatus of FIG. 10;

FIG. 12 is a side detail, shown in cutaway, of the jaw members of theelectrosurgical apparatus of FIG. 10;

FIG. 13 is a side detail of the jaw members of the electrosurgicalapparatus of FIG. 10 spaced apart about a layer of tissue;

FIG. 14 is a side detail of the jaw members of the electrosurgicalapparatus of FIG. 10 clamping a layer of tissue and transmitting currenttherethrough; and

FIG. 15 is a side detail of the jaw members of the electrosurgicalapparatus of FIG. 10 clamping a layer of tissue and radiating heattherethrough.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are describedhereinbelow with reference to the accompanying drawings. In thefollowing description, well-known functions or constructions are notdescribed in detail to avoid obscuring the present disclosure inunnecessary detail. Those skilled in the art will understand that theinvention according to the present disclosure may be configured for usewith either monopolar or bipolar electrosurgical systems and either anendoscopic instrument or an open instrument. It should also beappreciated that different electrical and mechanical connections andother considerations apply to each particular type of instrument.

FIG. 1 is a perspective view of an electrosurgical dissection system100. The electrosurgical system 100 includes an electrosurgicalgenerator 110 that supplies electrosurgical radio frequency (“RF”)energy to a bipolar electrosurgical pencil 120 via one or more coaxialcables 112 or transmission wires 113. Electrosurgical generator 110 mayinclude a number of user controls for varying the amplitude andwavelength of the energy supplied to electrosurgical pencil 120.Electrosurgical dissection system 100 and the intercooperatingrelationships of the various components are explained in greater detailin U.S. Publication No. 2006/0178667, the entire contents of which arehereby incorporated by reference.

Electrosurgical pencil 120 is configured for dissecting body tissue “T”(FIG. 4). Electrosurgical pencil 120 has an elongate body 121 defining alongitudinal axis “A” (FIG. 4) that narrows toward distal tip 128. Thebody 121 of electrosurgical pencil 120 may be thin and blade-like, ormay have any other desirable configuration. Distal tip 128 may bepointed, rounded, or blunt, and includes a portion of an activeelectrode 122 formed of an electrically conductive material such ascopper, silver, or gold. The formation of active electrode 122 will bedescribed in further detail below. Active electrode 122 is electricallycoupled to electrosurgical generator 110 through one or more coaxialcables 112. Additional transmission wires 113 may be power cables orleads suitable for electrical coupling of electrosurgical generator 110and electrosurgical pencil 120. Electrosurgical pencil 120 may include ahandle portion suitable for engagement by an operator, such as a pistolgrip, textured or contoured gripping surface, or may be configured forcoupling to a robotic arm or other tool (not shown). It is contemplatedthat such a handle portion may be detachable from the remainder ofelectrosurgical pencil 120.

Electrosurgical pencil 120 includes a pair of return electrodes 124 thatare laterally spaced along the body 121. Return electrodes 124 arecoupled to electrosurgical generator 110 through one or more coaxialcables 112. Return electrodes 124 may be placed on opposing surfaces ofthe body 121 and proximal of the distal tip 128, as shown, or may beplaced in any desirable location along the body 121 of electrosurgicalpencil 120. Alternatively, a single return electrode 124 may be present,or three or more return electrodes 124 may be placed along the body 121of electrosurgical pencil 120. Return electrodes 124 may be attached tothe body 121 of electrosurgical pencil 120 by stamping, by overmolding,by casting, by overmolding a casting, by coating a casting, byovermolding a stamped electrically conductive plate and/or byovermolding a metal injection molded plate or in other ways customary inthe art. Alternatively, electrodes may be placed by inserting hollowtubes of electrically conductive material into the body 121 ofelectrosurgical pencil 120, or by forming the body 121 ofelectrosurgical pencil 120 about hollow tubes of electrically conductivematerial (not shown). Electrodes may additionally be formed of a metalcoated with another metal having a higher electrical conductivity, suchas copper, silver, or gold.

The body 121 of electrosurgical pencil 120 is formed of a materialhaving a low electrical conductivity and thermal conductivity, and maybe formed of a synthetic resin, e.g., an amorphous polyamide such asavailable from Evonik Industries, under the trademark TROGAMID®, whichhas an electrical conductivity of 1.0·e⁻²⁰ [S/m] and a thermalconductivity of 0.26 [W/(m·K)]. Other materials having suitableproperties of a thermal and electrical insulator are contemplated forthe body 121 of electrosurgical pencil 120.

The body 121 of electrosurgical pencil 120 contains an insert 126 formedof a material having a low electrical conductivity and a high thermalconductivity, such as a ceramic material, for example, alumina (aluminumoxide), which has an electrical conductivity of 1.054·e⁻¹³ [S/m] and athermal conductivity of 28 [W/(m·K)]. By contrast, human tissue has anelectrical conductivity of about 0.512 [W/(m·K)]. Other materials havingsuitable properties of a thermally conductive electrical insulator arecontemplated for insert 126. The surface of insert 126 exposed on thebody 121 of electrosurgical pencil 120 is coated with a layer ofconductive material 123 (FIG. 3) forming the active electrode 122.Insert 126 and accompanying active electrode 122 may protrude from thebody 121 of electrosurgical pencil 120, as shown, or may be flush withbody 121.

Turning to FIG. 2, a cross-sectional view of the electrosurgical pencil120 taken along section line 2-2 of FIG. 1 is shown. Insert 126 may bedisposed along a pre-formed channel within body 121 of electrosurgicalpencil 120, or body 121 may be molded around insert 126. Alternatively,insert 126 may be attached to body 121 of electrosurgical pencil 120 byan adhesive, or may have intercooperating surface features with body121. Additionally, insert 126 may be centered about longitudinal axis A(FIG. 4), or may be offset relative to longitudinal axis A. Insert 126may be inserted to a partial depth through body 121, or may extend fullytherethrough. In such an embodiment, insert 126 would be sandwichedbetween two portions of body 121 (not shown).

Referring to FIG. 3, the formation of active electrode 122 on the body121 of electrosurgical pencil 120 (FIG. 1) is shown. Active electrode122 is formed of a layer of conductive material 123 having a highelectrical conductivity, such as copper, silver, or gold. Conductivematerial 123 is deposited along insert 126 electrosurgical pencil 120with a precision instrument 130 capable of delivering a flow of theconductive material 123, such as a micropen. Precision instrument 130ensures that the layer of conductive material 123 is deposited in aselected region on insert 126 to ensure that the discharge of RF energyfrom electrosurgical pencil 120 is concentrated about an area readilymanipulated by an operator to dissect desired sections of tissue T (FIG.4) while leaving other sections of tissue T unaffected.

Turning to FIG. 4, electrosurgical pencil 120 is shown prior toinsertion and spaced from a layer of tissue T. RF energy is suppliedfrom electrosurgical generator 110 (FIG. 1) through coaxial cable 112 toactive electrode 122 and flows to return electrodes 124. RF energy istransmitted from the return electrodes 124 through the coaxial cable 112or transmission wires 113 to electrosurgical generator 110, forming acompleted circuit. The RF energy is illustrated by current lines “C” isused to dissect tissue T.

Referring to FIGS. 5 and 6, the application of RF energy causes thedissection of tissue T through cutting or ablation such that a path iscleared allowing for advancement of the electrosurgical pencil 120through tissue T. As described above, the body 121 of electrosurgicalpencil 120 may be tapered or blade-like, and may cooperate withelectrodes 122, 124 to clear a path through tissue T. Electrosurgicalpencil may be inserted to a desired depth “D” in tissue T. The passageof current C from the active electrode 122 to return electrodes 124 alsoresults in the generation of thermal energy “H”. Thermal energy H isabsorbed and stored by the thermally conductive insert 126. When currentC is not passing from active electrode 122 to return electrodes 124after the electrosurgical generator 110 (FIG. 1) has been shut off orbetween cycles of AC power supply, thermal energy H is radiated tosurrounding tissue T and serves to cauterize tissue T or coagulate bloodflowing therefrom. Thus, the passage of current C from the activeelectrode 122 to return electrodes 124 and the resultant storage andrelease of thermal energy H from insert 126 serves the purposes ofdissecting and otherwise treating tissue T. Accordingly, electrosurgicalpencil 120 may be activated and inserted into tissue T to dissect asection of tissue T, while minimizing the loss of fluids such as bloodtherefrom and maintaining the integrity of the dissected tissue Tthrough cauterization.

Turning to FIGS. 7 and 8, an alternate embodiment of the presentlydisclosed electrosurgical pencil, designated 220, is shown.Electrosurgical pencil 220 is configured to be electrically coupled toan electrosurgical generator 110 (FIG. 1) through coaxial cable 112 andtransmission wires 113 (FIG. 1) as with electrosurgical pencil 120described above. Electrosurgical pencil 220 has a body 221 that includesa proximal section 222 formed of a thermal conductor such as alumina,and a distal section 224 formed of a thermal insulator made from asynthetic resin, e.g., an amorphous polyamide such as available fromEvonik Industries, under the trademark TROGAMID®. Other materials havingsuitable thermal properties are contemplated for proximal and distalsections 222, 224 of body 221. Body 221 of electrosurgical pencil 220may be tapered or otherwise configured, and may have a distal tip thatis sharpened, rounded, or blunt.

Active electrodes 226 and return electrodes 228 are disposed on the body221 of electrosurgical pencil 220. Active electrodes 226 and returnelectrodes 228 are formed in a substantially similar manner as theactive electrodes 122 and return electrodes 124 of FIG. 1 and may beplaced in any desirable pattern along body 221 of electrosurgical pencil220 such that the distribution of current C is optimized for incisioninto tissue T.

The thermal profile of electrosurgical pencil 220 differs from that ofelectrosurgical pencil 120 described above, in that thermal energy H isstored within the proximal section 222 of body 221. When current C isnot flowing between active and return electrodes 226, 228, thermalenergy H is released from the proximal section 222 of body 221 intosurrounding tissue T to treat tissue T through cauterization and tocoagulate blood flowing therefrom. Thus, electrosurgical pencil 220provides for dissection of tissue T through the use of RF energy, andproximal section 222 of body 221 is configured to store and releasethermal energy H in a manner such that tissue T is cauterized and bloodis coagulated in the wake of the advancement of distal tip 230.Electrosurgical pencil 220 allows for initial tissue penetration by thecurrent C flowing from active electrodes 226 to return electrodes 228,and the thermal profile of body 221 facilitates the smooth advancementof electrosurgical pencil 220 through tissue T by the release of thermalenergy H from proximal section 222 of body 221.

Turning to FIG. 9, an alternate embodiment of the presently disclosedelectrosurgical pencil, designated 320, is shown. Electrosurgical pencil320 is configured to be electrically coupled to an electrosurgicalgenerator 110 (FIG. 1) through coaxial cable 112 and transmission wires113 (FIG. 1) as with electrosurgical pencil 120 (FIG. 1) describedabove. Electrosurgical pencil 320 has a tapered elongate body 321 thatconverges toward a distal tip 328. Body 321 of electrosurgical pencil320 may be formed of a thermally conductive material such as stainlesssteel, though electrosurgical pencil 320 may be formed of othermaterials.

During the flow of current from active electrodes to return electrodesas described in the previous embodiments, thermal energy is generatedand stored in the body 321 of electrosurgical pencil 320. As thediameter of the body 321 of electrosurgical pencil 320 increases from adistal end toward the proximal tip 328, more mass is available forthermal energy storage towards the proximal end of the body 321.Accordingly, the thermal profile of electrosurgical pencil 320 is suchthat more thermal energy “H” is stored and released toward the proximalend of the body 321. Thus, electrosurgical pencil 320 is configured tostore and release thermal energy H in a manner such that tissue T (FIG.4) is cauterized and blood is coagulated in the wake of the advancementof distal tip 328. Electrosurgical pencil 320 allows for initial tissuepenetration by current flowing from active electrodes to returnelectrodes, as described in the previous embodiments, and the thermalprofile of body 321 facilitates the smooth advancement ofelectrosurgical pencil 320 through tissue by the increased release ofthermal energy H from a proximal section of body 321.

Turning now to FIG. 10, another embodiment of the present disclosure isshown. Electrosurgical system 200 includes an electrosurgical generator(not shown) such as electrosurgical generator 110 (FIG. 1), and anelectrosurgical dissection apparatus such as electrosurgical forceps 201for treating tissue. RF energy is supplied from electrosurgicalgenerator 110 (FIG. 1) to forceps 201 through coaxial cable 112.

The forceps 201 is configured to support an effector assembly 210 andgenerally includes a housing 202, a handle assembly 204, a rotatingassembly 206, and a trigger assembly 208 that mutually cooperate withthe end effector assembly 210 to grasp, seal and, if required, dividetissue. Electrosurgical forceps 201 also includes a shaft 212 that has adistal end 214 that mechanically engages the end effector assembly 210and a proximal end 216 that mechanically engages and is retained by thehousing 202.

Referring to FIGS. 11 and 12, end effector assembly 210 includes a pairof opposing jaw members 220 a, 220 b each having an electricallyconductive sealing plate 221 a, 221 b, respectively, attached theretofor conducting electrosurgical energy through tissue “T” (FIG. 13) heldtherebetween. More particularly, the jaw members 220 a, 220 b areconfigured for relative approximation and move from an open position toa closed position in response to actuation of handle assembly 204 (FIG.10). In the open position, the sealing plates 221 a, 221 b are disposedin spaced relation relative to one another. In a clamping or closedposition, the sealing plates 221 a, 221 b cooperate to grasp tissue Tand apply electrosurgical energy thereto.

Jaw members 220 a, 220 b are activated using a drive assembly (notshown) enclosed within the housing 202 (FIG. 10). The drive assemblycooperates with the handle assembly 204 to impart movement of the jawmembers 220 a, 220 b from the open position to the clamping or closedposition. Examples of handle assemblies are shown and described incommonly-owned U.S. Pat. No. 7,156,846 entitled “VESSEL SEALER ANDDIVIDER FOR USE WITH SMALL TROCARS AND CANNULAS” the entire contents ofwhich are hereby incorporated by reference herein in its entirety.

Sealing plates 221 a, 221 b of jaw members 220 a, 220 b are formed of asynthetic resin material having a low electrical conductivity andthermal conductivity, e.g., a amorphous polyamide such as available fromEvonik Industries, under the trademark TROGAMID®′, which has anelectrical conductivity of 1.0·e⁻²⁰ [S/m] and a thermal conductivity of0.26 [W/(m·K)]. Other materials having suitable properties of a thermaland electrical insulator are contemplated for the sealing plates 221 a,221 b of jaw members 220 a, 220 b. In embodiments, other portions or theentirety of jaw members 220 a, 220 b may be formed of such materials.

Jaw members 220 a, 220 b contain at least one insert 226 a, 226 b formedof a material having a low electrical conductivity and a high thermalconductivity, such as a ceramic material, for example, alumina (aluminumoxide), which has an electrical conductivity of 1.054·e⁻¹³ [S/m] and athermal conductivity of 28 [W/(m·K)]. By contrast, human tissue has anelectrical conductivity of about 0.512 [W/(m·K)]. Other materials havingsuitable properties of a thermally conductive electrical insulator arecontemplated for inserts 226 a, 226 b. Inserts 226 a, 226 b may beconfigured as an elongated strip of material. The surface of inserts 226a, 226 b is exposed on the respective sealing plate 221 a, 221 b of eachjaw member 220 a, 220 b. Inserts 226 a, 226 b may be disposed along apre-formed channel within each jaw member 220 a, 220 b, or each jawmember 220 a, 220 b may be molded around respective inserts 226 a, 226b. Alternatively, inserts 226 a, 226 b may be attached to each jawmember 220 a, 220 b by an adhesive, or may have intercooperating surfacefeatures with each jaw member 220 a, 220 b. Inserts 226 a, 226 b may beinserted to a partial depth through each jaw member 220 a, 220 b, or mayextend fully therethrough. In such an embodiment, inserts 226 a, 226 bwould be sandwiched between adjacent portions of each jaw member 220 a,220 b (not shown).

Inserts 226 a, 226 b are coated with a layer of conductive material 223,forming an active electrode 228 or a return electrode 229. Activeelectrode 228 is disposed opposite return electrode 229 to effectbipolar RF transmission, as will be described further below. Inserts 226a, 226 b and the associated conductive material 223 may protrude fromthe sealing plates 221 a, 221 b of jaw members 220 a, 220 b, as shown,or may be flush with jaw members 220 a, 220 b.

An additional insert 227 a, 227 b may be disposed on a front face 222 a,222 b of each respective jaw member 220 a, 220 b, as shown, and may beconfigured as a strip of alumina or another similar material asdescribed above. Inserts 227 a, 227 b may be coated with a layer ofconductive material 223 as described above, and may be configured tooperate as the active electrode 228 or the return electrode 229.

Referring to FIGS. 13-15, the application of RF energy causes thesealing of tissue T. As noted above, jaw members 220 a, 220 b may beapproximated to a closed configuration to clamp tissue T. It should benoted that two mechanical factors play an important role in determiningthe resulting thickness of the sealed tissue T and the effectiveness ofthe seal, i.e., the pressure applied between the opposing jaw members220 a, 220 b (between about 3 kg/cm² to about 16 kg/cm²) and the gapdistance “G” between the opposing sealing plates 221 a, 221 b of the jawmembers 220 a, 220 b, respectively, during the sealing process (betweenabout 0.001 inches to about 0.006 inches). One or more stop members (notshown) may be employed on one or both sealing plates 221 a, 221 b tocontrol the gap distance. A third mechanical factor has recently beendetermined to contribute to the quality and consistency of a tissueseal, namely, the closure rate of the electrically conductive surfacesor sealing plates 221 a, 221 b during electrical activation.

The passage of current C between the active electrodes 228 and returnelectrodes 229 also results in the generation of thermal energy “H”.Thermal energy H is absorbed and stored by the thermally conductiveinserts 226 a, 226 b, 227 a, 227 b (FIG. 12). When current C is notpassing between the active electrodes 228 and return electrodes 229after the electrosurgical generator 110 (FIG. 1) has been shut off orbetween cycles of AC power supply, thermal energy H is radiated tosurrounding tissue T and serves to cauterize tissue T or coagulate bloodflowing therefrom. Thus, the passage of current C between the activeelectrodes 228 and return electrodes 229 and the resultant storage andrelease of thermal energy H from inserts 226, 227 serves the purposes ofsealing or otherwise treating tissue T. Accordingly, electrosurgicalforceps 201 may be activated and inserted into tissue T to seal asection of tissue T, while minimizing the loss of fluids such as bloodtherefrom and maintaining the integrity of the dissected tissue Tthrough cauterization.

While several aspects of the disclosure have been shown in the drawings,it is not intended that the disclosure be limited thereto, as it isintended that the disclosure be as broad in scope as the art will allowand that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular aspects. Those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

What is claimed is:
 1. An electrosurgical pencil comprising: a proximalportion formed of a thermal conductor including: a first activeelectrode disposed on the thermal conductor, and a first returnelectrode disposed on the thermal conductor; and a distal portion formedof a thermal insulator including: a second active electrode, differentfrom the first active electrode, disposed on the thermal insulator, anda second return electrode, different from the first return electrode,disposed on the thermal insulator, wherein the thermal conductor isconfigured to store thermal energy when radiofrequency energy is passingfrom the first active electrode to the first return electrode andcauterize tissue by releasing the stored thermal energy whenradiofrequency energy is not passing from the first active electrode tothe first return electrode.
 2. The electrosurgical pencil of claim 1,wherein the distal portion includes a distal tip, wherein a shape of thedistal tip is one of sharpened, rounded, or blunt.
 3. Theelectrosurgical pencil of claim 1, wherein the first active electrode isformed of one of copper, silver, or gold.
 4. The electrosurgical pencilof claim 1, wherein the thermal insulator is formed from an amorphouspolyamide.
 5. The electrosurgical pencil of claim 1, wherein the thermalconductor is formed from alumina.
 6. The electrosurgical pencil of claim5, wherein the first active electrode is formed from one of copper,silver, or gold.
 7. The electrosurgical pencil of claim 1, wherein thefirst active electrode is formed from a coating of conductive material.8. An electrosurgical dissection system comprising: an electrosurgicalgenerator configured to generate electrosurgical energy; anelectrosurgical pencil comprising: a proximal portion formed of athermal conductor including: a first active electrode disposed on thethermal conductor, and a first return electrode disposed on the thermalconductor; a distal portion formed of a thermal insulator including: asecond active electrode, different from the first active electrode,disposed on the thermal insulator, and a second return electrode,different from the first return electrode, disposed on the thermalinsulator, wherein the thermal conductor is configured to store thermalenergy when radiofrequency energy is passing from the first activeelectrode to the first return electrode and to cauterize tissue byreleasing the stored thermal energy when radiofrequency energy is notpassing from the first active electrode to the first return electrode;and a cable connecting the electrosurgical generator to theelectrosurgical pencil.
 9. The electrosurgical system of claim 8,wherein the distal portion of the electrosurgical pencil includes adistal tip, wherein a shape of the distal tip is one of sharpened,rounded, or blunt.
 10. The electrosurgical dissection system of claim 9,wherein the first active electrode is formed from a coating ofconductive material.
 11. The electrosurgical dissection system of claim10 wherein the first active electrode is formed from one of copper,silver, or gold.
 12. The electrosurgical dissection system of claim 8,wherein the first active electrode is formed of one of copper, silver,or gold.
 13. The electrosurgical dissection system of claim 8, whereinthe thermal insulator is formed from an amorphous polyamide.
 14. Theelectrosurgical dissection system of claim 8, wherein the thermalconductor is formed from alumina.